Tension mechanism of straw-plait-sewing machines.



E. WISEMAN.

TENSION MECHANlSM 0F STRAW PLAIT SEWING MACHINES.

APPLICATION FILED FEB. 3. 1914.

1,137,250. Patented Apr. 27, 1915.

THE NORRIS PETERS Co.. PHOTO-LITHO. WASHINGTON, D4 C shifting the nmvrnnii wrsnivrnn, or moron, ENGLAND.

TENSION MECHANISM OF ,s'rRAw-rLArr-snwmc; MACHINES.

Specification of Letters Patent.

Patented lipr.27,1915.

Original application filed August 30, 1913, Serial No. 787,511. Divided and this application filed February I 1 3,1914. Serial No. 816,166. g

To all whom it may concern:

Be it known that I, EDMUND ,WISEMAN, a subject of His Majesty the King ofv Great Britain, residing at London Road, Luton, in the county of Bedford, England, have in.- vented certain new and useful- Improve; ments in or Relating tothe Tension Mechanism of Straw-Plait-Sewing Machines; and

V I do hereby declare the following to be a full, clear, ,and exact descriptionof the invention, such as will enable other s'skilled in the art to which it appertainstomake and use the same.

This invention has reference to that class of straw plait sewing machines wherein sewing implements or needles attached to a carrier beneath the work plate, are thrust upward through the work and cooperate with vone or more looping devices supported above and movable with the presser foot. Sewing machines of this class are described in my patents, Nos. 228711 and 565585 and also in J ohnsons British Patent No. 5926 of 1886. Myvinvention has particular relation to sewing machines of the class aforesaidprovided with intermittent tension mechanism whereby the tension is automatically opened and closed by a tension cam at appropriate periods'during each stitch, such for example as is described in my U. S. Patent No. 248023; and relates more especially to those sewing machines which are provided with variable lntermittent tension mechanism 41 such for example as is described in Johnsons 35 I said British patent, whereina tension cam is mounted and adjustable laterally on the main shaft and connected withthe devices for changing thefeed movement, so that by cam laterally the V stitch is altered, one of the operating inclines of said cam extending obliquely around the cam so that lateral movement of the latter will vary the timing of one of the closings of the tension by causing a different portion of this oblique incline to act on the tension lever which operates the tension proper.

The object of my'invention is to improve the quality of the work produced and to this end my invention consists in improvements in the said intermittent tension mechanism designed to give a more effective thread control and consisting principally in the provision of a tension cam designed to give a greater number of moreappropriately timed openings and closings of the tension during each stitch than heretofore.

In known intermittent tension mechanism, such for example as is described in my said Patent No. 243023 and also in Johnsons said British patent, the tension cam is furnished withinclines arranged to open and close the tension twice during every stitch vfor all.

lengths of stitches; a known modification of cam for variable intermittent tension mechanism adds inclines which give a further rapid opening and closing for the shorter stitches only. 9 f

According to my invention, with the object of drawing up all stitches vfrom the longest to the shortest in the most perfect manner possible, I provide the tension cam with inclines so arranged as to give four openings and fourclosings of the tension at the most appropriate times during every stitch, for stitches of all lengths, and I also,

in the case of a cam for variable intermittent tension mechanism, modify the contour of on the thread by the actof altering the stitch, and in lieu of'automatic means for changing the degree of tension I preferably use hand operated means, such as will be hereinafter described, whereby the degree of tension may be instantly altered and restored again to the exact degree to which it was originally adjusted by the screw tension stud. It is to-be understood that my improved tension cam, when adapted for variable intermittent tension, operates or is operated by the feed changing devices in the known manner, my invention being as before explained directed to causing the tension cam to give additional openings and closings of the tension during every stitch and to time sa1d openings and closings more appropriately and accurately.

In the annexed drawings in which similar lettersrefer to like parts in all the figures -Figure 1 is a part sectional plan view showing a sewing machine of the kind described embodying my improvements those.

' parts of the machine not necessary for a clear understanding of the invention being omitted. through Fig. 1., showing the tension cam and tension proper and the hand operated means for varying the degree of tension. Fig. 8 is an end View of my improved tension cam looking from the right. Fig. l'is a development of a portion of this cam.

My improvements'in'the intermittent tens sion mechanism are shown in the drawings as appl ed to variable intermlttent tenslon mechanism similar to that described in erally on the main shaft D by the lever N,

see Figs. 1 and 2, and adapted to shift the position of the variable feed eccentric M to change the length of stitch by means of the lever 107 in the known manner. V

' 88 is the tension lever whose roller is held spring pressed against the camJ, and 809 is a screw carried by lever 88 the end of vwhichscrew atthe proper times is caused to strike the end ofthe tension stud 84 and open the tension, also in the known manner.

My improved tension cam is designed as before stated to, give at themost appropriate times during each stitch, four openings and four closings. of the tension, and to this end is constructed with eight inclines, as seen in Figs. 3 and 4:. These 1110111168 316 deslgnated I by the numerals l to 8, the odd numbers indicating the inclines which open the tension and the even numbers the inclines for closing it. Inclines l to 7 extend parallel with the cam axis, and incline 8, which gives the variable closing of the tension 1 extends obliquely around the cam. The longer stitches are produced when the .side marked L (Fig. 4) .of the cam is opposite the roller of the tension lever 88, and the shorter stitchesare produced when the side marked S is opposite said tension lever roller. The cam makes one complete revolution for every stitch, and hasits inclines so spaced and arranged, and is so set'upon its shaft, thatv the timings of the openings and closings 'of the tension. will. be substantially as follows Incline 1 opens the tension for all; lengths of stitch just before theneedle eye reaches the top of the needle plate, the tension remaining open long enough to prevent any strain on the thread while the eye of the needle is passing through the work; The roller of the tension lever 88 now arrives at incline '2 and the tension closes and remainsclosed Fig, 2 is a transverse section until theneedles' approach thetopof their stroke,.,when incline 3 opens the tension which is 'kept. open until the looper and threader have respectivelyengaged their loops when" the roller'of tension lever 88 reaches incline 4 after which the tension is closed-and remains closed until" the looper commences its retreat, this time'of closing materially assisting indrawing up the loop.

which are usually sewn with theseshorter stitches.- Incline 7 now opens the tension and the time it remains open will be governed by movement of the cam laterally on its shaft, which causes the roller of thetension lever to travel across different parts of the closing incline 8 which extends obliquely around the cam. It will be noted that this incline 8 is not continuous, as inthe known tension cam, but is stepped about midway of its length, and this special contour assists materially in the drawing up of the stitches intermediate of the'short'est and longest. The incline 8 closes thet'ension'for the shortest stitch at about the time the feed commences its advance, and for the longest stitch slightly before the feed-has completed its travel. The cycle now-recommences.

With tension mechanism arranged and adapted to operate as above described I find as before stated that it is neither neces sary nor advisable to employ means for antomatically varying the degree of tension by the act of changing the length of stitch, and Iprovide means for altering the degree of tension by hand and for instantly restoring the original degree of tension determined by the usual screw tension stud;

The tension proper shown in the drawings is similar to that'shown' in J ohnsonssaid British patent, butin lieu of connecting the pin 228, which extends from the sliding sleeve 81 of the tension through a slot in the sleeveboss, by a link with an arm 'of the tension cam shifting lever N, I pivot inside the casing of the machine a lever 0 carrying at its free end an incline '0 adapted tobear on the said pin 228 of the sliding sleeve 81, and to the exterior of the casing I pivot the hand'lever'p. A pin p extends fromthe lever 0 through a slot inthe casing and engages in a notch in the lever p, whereby the two levers p, and 0- move together. Onmovstop ing the hand lever 72 the incline 0 acting on the pin'228 will move the sleeve 81 endwiseto compress the tension spring 85 and increase the degree of tension, and on moving back the hand lever to its original position, the slot in the casing constituting a to limit its movement, the original degree of tension determined by the. screw tension stud 84 will be restored.

Although I have described with reference to and shown in my drawings my improved tension cam as arranged for and applied to a well known kind of variable intermittent tension mechanism, it-is tobe understood that a tension cam arranged to give four openings and four closings of the tension during every stitch, at the times stated, may with advantage be used in a sewing machine of the class described having mechanism which is intermittent without being variable and wherein the'tension cam does not I 'move laterally on itsshaft when the stitch length is altered; In this case the oblique stepped incline 8 would .be dispensed with and an incline parallel with the cam axis substituted therefor, said incline being arranged to close the tension for all lengths of stitches at sometime between the commencement of the feed advancejiand the completion of its travel, accordingto the length of stitch being used;

The tension mechanlsm above described is very advantageously used in conjunction with the controller mechanism locking means described in the specification accompanying my application for U.

787511, filed August 30, 1913 of which the present application is a'division.

What I claim and desire to secure by Letters Patent in the United States is z- 1. A sewing machine, embodying therein thread tensioning mechanism, and controlling means therefor comprising a revoluble cam having a series of eight successive peripheral inclines, seven of said inclines extending parallel with the cam axis and one of said inclines extending obliquely around said cam, said inclines being adapted to alternately open and close said tensioning mechanism eight times during each revolution of said cam.

2. A sewing machine, embodyingtherein thread tensioning mechanism, and control- Gopies of this patent may be obtained for revolution of said cam to relatively loose on the short top portion ofv ling means therefor comprising a revoluble cam having a series of eight successive peripheral inclines, seven of said inclines extending parallel with the cam axis and one of said inclines extending obliquely around said cam and being stepped about midway of its length, said inclines being adapted to alternately open and close said tensioning mechanism eight times during each revolution of-said cam.

3. A sewing machine, embodying therein thread tensioning mechanism, controlling means therefor comprising a revoluble cam having a series of eight successive peripheral inclines, seven of said inclines extending parallel with the cam axis and one of said inclines extending obliquely around said cam and being stepped about midway of its length, said inclines being adapted to alternately open and close said tensioning mechanism eight times during each revolution of said cam, and means for shifting said cam laterally whereby said last named incline varies the timing of a predetermined closing of said tensioning mechanism.

4. In a straw plait sewing machine, the combination with thread tensioning mechanism, of a revoluble tension cam cooperating therewith, and means on the periphery of said cam for opening and closing said tensioning mechanism eight times during each produce stitches the stitch and relatively tight on the long under portion of the stitch. S. Patent 5. In a straw plait sewing machine, the combination with thread tensioning mechanism, of a revoluble tension cam cooperating therewith, and a series of successive inclines on the periphery of said cam adapted to open and close said tensioning mechanism'eight times during each revolution of said cam to produce stitches relatively loose on the short top portion of the stitch and relatively tight on the long under portion of the stitch. V

In testimony whereof I have hereunto set my hand in the presence of two witnesses.

EDMUND WISEMAN.

Witnesses! A. E. ALEXANDER, EDITH HALL.

five cents each, by addressing the Commissioner 01} Il-Iatents,

Washington, D. O, 

